Objective  To investigate the effect of sirtuin 5 (SIRT5) on glucose metabolism and colorectal cancer cell proliferation and its possible mechanism, as well as the expression level of SIRT5 and glucose-6-phosphate dehydrogenease (G6PD) in colorectal cancer tissues.

  Methods  Western blot was used to detect SIRT5 protein expression level in human colorectal cancer cell lines-HCT116 and HT29. SIRT5 plasmid and SIRT5 siRNA were constructed and transfected into colorectal cancer cell lines with low SIRT5 expression and high SIRT5 expression, respectively. Glucose and lactic acid content in the culture medium was determined with glucose oxidase and colorimetric methods, respectively. The proliferation ability of transfected cells was determined with a clonal formation assay. CCK-8 assay was performed to detect the viability of transfected cells. The regulatory effects of SIRT5 on G6PD mRNA and protein expression levels were evaluated with RT-PCR and Western blot. SIRT5 and G6PD expression levels in colorectal cancer tissues were detected with immunohistochemistry.

  Results  Glucose concentration in the culture medium increased significantly, and the lactic acid concentration in the culture medium was decreased significantly. The cell activity and proliferation ability of colorectal cancer cells were significantly decreased after SIRT5 was knocked down; the glucose concentration in the culture medium decreased significantly, and the lactic acid concentration in the culture medium was significantly increased. Cell activity and proliferation ability of colorectal cancer cells was significantly enhanced after SIRT5 was over expressed. Additionally, SIRT5 positively regulated the expression of G6PD. Co-transfection of SIRT5-siRNA and G6PD plasmid restored glucose metabolism and the growth and proliferation ability of colorectal cancer cells compared to that of SIRT5-siRNA transfection alone. The expression level of SIRT5 and G6PD in colorectal cancer tissues was significantly higher than that in paracancerous tissues.

  Conclusions  SIRT5 and G6PD were highly expressed in colorectal cancer tissues. Furthermore, SIRT5 promotes glucose metabolism and colorectal cancer cell proliferation by regulating G6PD.